Interestingly enough, St. Bernadette did not know she was seeing the Blessed Virgin Mary when the apparitions began.
All she knew was that she saw a beautiful young lady dressed in white, with a blue sash around her waist.
St. Bernadette's parents and siblings were even more skeptical, thinking that the lady was a soul from purgatory, or possibly a demon.
The next time they visited the grotto, St. Bernadette and her siblings were prepared to test the vision.
Holy water
One of the first tests St. Bernadette performed was sprinkling the vision with holy water.
The 1872 book Our Lady of Lourdes recounts this first test, which happened the next time St. Bernadette saw Our Lady:
The little girls only perceived the desert rock and the branches of sweet briar which descended...where Bernadette contemplated an unknown being. Nevertheless, the countenance of Bernadette was such that there were no means of doubting. One of the children placed the bottle of holy water in the hands of her who saw.
St. Bernadette then approached the vision and armed herself with the holy water:
Then Bernadette remembering what she had promised, arose and shaking, quickly and with several repetitions, the little bottle sprinkled the wonderful lady, who quite graciously remained at some paces before her in the interior of the niche.
St. Bernadette then said, "If you come on the part of God, approach."
Our Lady "bowed several times and advanced almost to the end of the rock. She seemed to smile at the precautions of Bernadette and at her weapons of war and at the sacred name of God her countenance lighted up."
Still slightly afraid, St. Bernadette proclaimed, "If you come on the part of the devil, begone."
Our Lady did not leave until St. Bernadette finished praying her Rosary.
Eventually St. Bernadette would ask the Lady what her name was, and she answered, "I am the Immaculate Conception."
This was the final confirmation for St. Bernadette that the Lady she saw was not a demon, but the Blessed Virgin Mary.
